I just put new tile down in my bathroom. They are a tile mosaic being attached to cement board. I used a standard thin set mortar. I followed the instructions for making the mortar exactly. However throughout the process the mortar got dry. I would add water and it seemed to help however the tiles with added water did not stick very well and some of them are coming up. Do I need to rip all of them up and start over or can I get away with pulling up the looser ones and reattach?
Anything already loose has to come up and be reinstalled. You can pull up just the bad sections, and keep the 'good' ones in place, provided you remove all the old thin-set. Otherwise, when you reinstall with new thin-set you'll be slightly higher.
It sounds like you had too dry of a mix to start with and took a long time to lay the tile. Also possible that you had old or cheap thin-set mix. I've noticed that the $5 a bag stuff tends to dry out quickly while the slightly more expensive multipurpose that runs around $15 a bag is more forgiving.
It's also possible they mixed too much material for the speed at which they could lay the tile. Mix smaller batches if that's the case.
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